IN THE MYSORE STATE. 5 



Assuming the carbonic acid to be present in the form of breun- 

 nerite, the sulphur as pyrite and the remainder of the iron mostly 

 as magnetite, we get the following mineral composition of the 

 matrix : — 



Breunnerite 

 Pyrite 

 Magnetite . 

 Talc and serpentine 



• 10-5 



0'2 



. io - o (approx.) 



• 79'3 ( » ) 



IOO"00 



Bulk composition. 



Combining these two analyses — that of the matrix with that of 

 the breunnerite phenocrysts — in proper proportion, we obtain a 

 bulk analysis for the rock of — 



Silica . 



Iron oxide (Fe 3 

 Magnesia . 

 Carbonic acid 

 Water 



,) 



J 7*3 

 127 



35"° 



20'0 



S'o 



IOO'O 



Assuming the rock to be the result of the alteration of an olivine 

 (dunite) magma, on which carbonic acid and water have acted, we 

 can, by the removal of these compounds, calculate the approximate 

 proportions of the three main constituents of the dunite magma. 

 Thus, removing the carbonic acid and water and calculating to ico, 

 we obtain :— 



Silica 



, 



• 36 - 4 



Iron oxide (Fe 3 Oj 



. 



. 169 



Magnesia . 



. 



. 467 



IOOO* 



( 5 ) 



